An in vitro model for culturing human and non-human beta cells was established for testing the capacity of viruses to infect beta cells. Using a double-label immunofluorescent antibody technique with insulin as a marker for functioning beta cells and viral antigen as a marker for mumps infection, it was shown that human beta cells could be infected by mumps virus. The capacity of other viruses to infect human and rhesus monkey beta cells is presently being tested. Studies on the induction of diabetes in mice infected with the M-variant of encephalomyocarditis virus showed that the tropism of the virus for pancreatic beta cells is genetically controlled and that there is a good correlation between viral replication, beta cell damage and hyperglycemia. BIBLIOGRAPHIC REFERENCES: Ross, M.E., Onodera, T., Brown, K.S. and Notkins, A.L.: Virus-Induced Diabetes Mellitus. IV. Genetic and Environmental Factors Influencing the Development of Diabetes Mellitus after Infection with the M-Variant of Encephalomyocarditis Virus. Diabetes, 25:190-197, 1976. Yoon, J.W. and Notkins, A.L.: Virus-Induced Diabetes Mellitus. VI. Genetically Determined Host Difference in the Replication of Encephalomyocarditis Virus in Pancreatic Beta Cells. J. Exp. Med., 143:1170-1185, 1976.